The utility model discloses a robot arm is used in vehicle door anti -collision rod welding, it includes the control electronic box of terminal surface under the supporting seat, the interface that charges is installed to the preceding terminal surface electrical property of control electronic box, switch is installed to the top electrical property that the preceding terminal surface of control electronic box lies in the interface that charges, and the lower terminal surface mounting screw of controlling the electronic box has the base, the up end of supporting seat rotates installs the back shaft no. One, and the up end of back shaft one side is provided with the back shaft no. Two, the one end that a back shaft was kept away from to the inside of no. Two back shafts is provided with evenaxle, and the surface that links the axle has cup jointed the soldered connection, the inside of soldered connection has been seted up and has been connect the hole, and the external surface thread of soldered connection installs thread disc. It can improve the stability that the soldered connection used, prevents that the spark that the welding produced from splashing everywhere, injures peripheral staff, improves the security of robot arm welded to can carry out the spacing and fixed of soft metal heat shield.